Gas discharge lamps are often used to produce ultraviolet radiation at wavelengths suitable for killing small microbes or germs. Ultraviolet radiation has been used to kill microorganisms by destroying their DNA. Germicidal protection using ultraviolet radiation is a safe and proven technology that helps kill bacteria, mold spores and viruses. The band of wavelengths that provide a germicidal action is often referred to as UVC, and is generally in the range of 250 nanometers. It is often desirable to produce a germicidal lamp that has the capability of emitting multiple bands of ultraviolet radiation or a broadband of ultraviolet radiation suitable for germicidal purposes. In the past, this has been accomplished by combining different types of glasses in a single lamp that transmits different wavelengths of ultraviolet radiation.
FIG. 1 illustrates one such prior lamp. FIG. 1 schematically illustrates a germicidal lamp 10 having end caps 12 and 14. Placed at either end of the lamp is a stem 16 and 18 for holding leads 20 and 22 supporting a filament 24 and 26. Electrical contact pins 34 and 36 provide an electrical contact through the leads 20 and 22 to the filament or electrodes 24 and 26. A glass envelope or tube is formed of two different types of glass separated by a seam or transition section 32. A first glass tube section 28 is comprised of doped quartz, which transmits ultraviolet radiation of approximately 254 nanometers. A second glass tube or portion 30 comprises quartz that transmits ultraviolet radiation at a wavelength of approximately 185 nanometers. Accordingly, a germicidal lamp having a conventional construction is formed.
In an effort to form a germicidal lamp that can be connected at a single end, a different construction has been made, as illustrated in FIG. 2. In FIG. 2, the germicidal lamp 110 is U-shaped and has end caps 112 and 114 adjacent each other with contact pins 134 and 136. The first glass 128 and the second glass 130 are divided by a seam or transition portion 132. Accordingly, a different type of glass is formed on each leg of the U-shaped germicidal lamp 110.
The germicidal lamps having a seam axially combining two different glass tubes are often difficult to manufacture and align. Also, while these lamps have been useful in providing multiple wavelengths of ultraviolet radiation to provide an effective germicidal action, their size and structure do not readily facilitate widespread use or in applications where a smaller or more compact structure is desired. Additionally, relatively high-powered lamps requiring larger diameter tubing are often difficult to accommodate in a small or compact size. Therefore, there is a need for a compact germicidal lamp that can accommodate glass tubes or cylinders having a relatively large diameter and that may be more easily fabricated.